While advances in the general lighting technology are heavily publicised, it is easy to overlook the similar advances that have been made in emergency lighting. James Beresford of Mackwell highlights the key factors for specification
Like most lighting technologies, emergency lighting has undergone some significant changes in recent years; particularly in relation to automatic monitoring and testing, use of LED light sources and the emergence of wireless communications. Wider use of LEDs won’t come as a surprise to Electrical Review readers but automatic monitoring and testing, as well as wireless communications, may not be so familiar – and they have an important role to play.
The basics remain the same though. The fundamental purpose of emergency lighting, is to come on automatically in the event of a power failure. This ensures that light levels are sufficient for people to find their way to safety.
The major differences between general and emergency lighting, is that safety is paramount and other factors, such as energy efficiency, are secondary considerations. Nevertheless, the introduction of LED light sources for emergency lighting has clearly resulted in a reduction in the power consumption of these systems, resulting in financial and environmental benefits for end users. The main financial savings, though, arise from the introduction of automated systems and their ability to simplify monitoring, testing and ongoing maintenance. These systems are discussed in more detail below.
Another consideration, and one that is often overlooked, is the visual appearance of the emergency lighting fittings. It is probably true to say that in the past, compliance with emergency lighting legislation has often been achieved at the expense of the aesthetics. Many luminaire manufacturers are now introducing standalone LED emergency fittings that complement their general lighting products so that aesthetics do not need to be sacrificed for the sake of compliance.
The basic elements relating to emergency lighting are ‘maintained’ or ‘non-maintained’. Maintained emergency lighting is on all of the time and stays on if the power fails. It would typically be used in public places where people may not be familiar with exit routes.
Non-maintained emergency lighting only comes on when the power fails and is typically found in workplaces where people are more familiar with escape routes.
The emergency lighting is powered by a battery system, which may be self-contained (located in or near the light fitting) or a central battery system serving a number of luminaires.
Emergency lighting products can be classified as standalone (e.g. illuminated exit signs or bulkhead luminaires) or a converted mains luminaire that contains emergency lighting components to run the luminaire; albeit at a reduced output from the battery if the power fails. Most luminaire manufacturers will offer an emergency option within a product portfolio. Aesthetically it looks the same but has the added components for emergency operation.
Monitoring, self-testing and control
Given the important role of emergency lighting in facilitating safe evacuation of the building, it’s quite surprising that the maintenance of such systems is often overlooked by the building operator. Yet there are legislative directives for emergency lighting that are implemented by Building Control officers and emergency lighting is a legal obligation.
In some cases, the building will require a licence from the local fire authorities and, in order to satisfy the requirements of this license, maintenance and testing log books must be kept and made available for inspection. This places an onus on the building operator to ensure that the emergency lighting is regularly monitored and tested.
The old way to test the lighting system was to isolate the mains power and monitor the emergency lighting by walking around the area - making sure all fittings worked and met the required duration. This was clearly a laborious and costly task and a major drain on maintenance resources in large buildings.
Control technologies have been used to try and ease this burden for the building operator. The introduction of self-testing emergency luminaires, helped to reduce the workload associated with legislative compliance. These systems routinely test all the fundamental aspects of the emergency lighting luminaire, where an integral LED for example, might flash to indicate a problem.
These systems still required somebody to walk around the building and check each indicator individually.
The next development was a reporting system, providing centralised monitoring and testing of the emergency lighting. Some lighting companies use their own proprietary control protocol for this; however, using an open protocol such as DALI as the basis for a monitoring system is beneficial, not least because it is the protocol that is most commonly used with general lighting schemes as well.
These reporting systems can be operated with or without a permanent connection to a computer. For relatively small stand-alone sites there is generally no need for a permanent connection, just the ability to connect one for configuration, viewing, and printing reports will usually be sufficient. In larger buildings, or for monitoring multiple sites, a permanent software interface is ideal. This will flag up faulty light sources, batteries and components so that any issues can be quickly remedied.
When installing a monitoring and reporting system there is clearly an additional cost to cover the data wire installation, the commissioning and the extra cost of the components. However, these costs are no more than standard controlled lighting interfaces and the chances are that the wiring infrastructure is already in place for the mains lighting.
Importantly, in terms of evaluating the return on investment, it is essential to compare the cost of a monitoring and reporting system with that of employing somebody to patrol the building on a regular basis and visually monitor each emergency luminaire individually. The same principle applies where a facilities management company is engaged to look after emergency lighting compliance. When such comparisons are made there is typically a very quick return on investment in centralised monitoring and reporting.
A more recent development that is set to have a positive impact on costs, is the introduction of wireless emergency lighting systems that do not require a separate data bus. This reduces the cost of installation and commissioning and also makes it easier to retrofit in existing buildings. It also reduces the risk of errors associated with installation of communication cables.
A key consideration in this respect is not to lose sight of the safety-critical aspects of the system; any mobile app or wireless communication system must take this into consideration. Consequently, the system should have a built-in contingency that ensures the luminaires default to standard auto-test if the wireless network fails.
Until recently, it has been deemed acceptable to have unsightly emergency lighting fixtures, as they are often viewed as a functional item with little thought for the aesthetics. Indeed, specifiers and designers will often leave it to the contractor to source and install a compliant system without providing any input on the visual aspects. To some extent, lighting manufacturers have also been guilty of not giving enough consideration to the design of their emergency luminaries.
This situation is changing as building operators become more demanding and the lighting manufacturers address that demand with more attractive designs. The current trend is towards standalone LED solutions and many luminaire manufacturers are now recognising that their emergency portfolio can be an integral part of their lighting package – and are giving this aspect more serious consideration.
It is important that specifiers play a more active role in the choice of emergency lighting, as a strong specification will ensure that the emergency system complements the overall design while also providing the required performance and legislative compliance.
Electrical engineers should also consider system performance and reliability. In this respect, it makes sense to engage in a detailed discussion with the luminaire manufacturer in relation to the components that are used. For example, the LED drivers can make a significant difference to the overall performance and longevity of the emergency luminaires.